V1.0

* New text for the home page
* Announcement
* Extracted install instructions from getting started

/cc @alco @ericmj please review!
IMO this sections is missing the definition of what v1.0.0 means in terms of stability and compatibility. Just saying it's semver is not enough, unless every single user facing piece of code is going to remain there until 2.0.

Not saying we should copy, but I find this [post on Go](https://golang.org/doc/go1compat) a very important step towards encouraging people to start using the language and having some sort of safety net – a promise that user code will work without changes for the foreseeable future.